KABUL, Afghanistan &

Afghan police mistook U.S. troops on a nighttime mission for Taliban fighters and opened fire on them early today, prompting U.S. forces to return fire and call in attack aircraft. Seven Afghan police were killed.




Gunmen on motorbikes, meanwhile, killed two schoolgirls today in central Afghanistan, as U.S.-led coalition and Afghan troops killed more than 24 suspected Taliban fighters during a battle in the south on Monday, officials said.




President Hamid Karzai's spokesman said the deaths of the Afghan police were "a tragic incident" caused by a lack of communication.




"The police forces were not aware of the coalition's operation," said spokesman Karim Rahimi. "The police checkpoint in the area thought that they were the enemy, so police opened fire on the coalition, and then the coalition thought that the enemies were firing on them, so they returned fire back."




The commander at the remote checkpoint in the eastern province of Nangarhar, Esanullah, who goes by one name, said U.S. gunfire and helicopter rockets killed seven policemen and wounded four.




Maj. Chris Belcher, a spokesman for the U.S.-led coalition, said a combined coalition-Afghan force was ambushed by small arms fire and rocket-propelled grenades from two sides while on the way to conduct an operation against a suspected Taliban safe house.




"Afghan and coalition forces took incoming fire and they responded to it," Belcher said. The forces called in air support, he said.




A policeman at the remote checkpoint said police called out for the approaching U.S. forces to halt.




"I thought they were Taliban, and we shouted at them to stop, but they came closer and they opened fire," said Khan Mohammad, one of the policemen at the post. "I'm very angry. We are here to protect the Afghan government and help serve the Afghan government, but the Americans have come to kill us."




Rahimi said the incident was being investigated and showed why Karzai has repeatedly called for increased cooperation and communication between Afghan and international troops, which would also help solve the ongoing problem of civilian casualties in Afghanistan.




In Nangarhar province in March &

the same province of Tuesday's police shootings &

19 civilians were killed and 50 wounded by U.S. Marines Special Operations Forces who fired on civilians while speeding away from the site of a suicide bomb attack, casualties that sparked angry protests and denunciations of the U.S. presence there.




A U.S. military commander later determined that the Marines used excessive force.




The International Committee of the Red Cross on Tuesday said the impact of violence on civilians in Afghanistan is worse now than it was a year ago.




Pierre Kraehenbuehl, the ICRC's director of operations, said fighting between armed opposition groups and the Afghan army supported by international forces had intensified significantly in the south and east of the country since 2006 and was spreading to the north and west.




"Civilians suffer horribly from mounting threats to their security," such as increasing numbers of roadside bombs, suicide attacks and airstrikes, he said in a statement.




In central Logar province, gunmen on two motorbikes opened fire on students leaving an all-girls school, killing two schoolgirls and wounding six others, said Education Minister Mohammad Hanif Atmar.




In the southern Kandahar province, U.S.-led coalition and Afghan troops killed more than 24 suspected Taliban fighters during an eight-hour battle in Shah Wali Kot in southern Kandahar province, the coalition said Tuesday.




The troops were ambushed by militants, who retreated after several of their fighters were killed. A force of some 30 Taliban later attacked the same coalition convoy, who called in airstrikes on a compound and a vehicle, killing "over two dozen enemy fighters," the coalition said.




Violence has spiked in Afghanistan in recent weeks. More than 2,300 people have died in insurgency-related violence this year, according to an Associated Press count based on U.S., NATO and Afghan figures.